the diameter of the circular garden is 20 ft

a contractor is developing plans to build a 5 foot wide walkway around the garden thus the diameter of the garden together with the walkway will be 20 + 2*5 = 30 ft

the area of the walkway = the area of the garden together with the walkway - the are of the circular garden only

the area of the walkway = (30/2)^2*pi - (20/2)^2*pi = pi(15^2 - 10^2) = 125*pi

the area of the walkway = 125*pi

pi = 3.14

the area of the walkway = 125*3.14

the area of the walkway = 392.5 ft^2